Diversity of NC10 Bacteria and ANME-2d Archaea in Sediments of Fault Zones at Lake Baikal

Anna Lomakina,Tatyana Pogodaeva,Gennady Kalmychkov,Tamara Zemskaya,Svetlana Chernitsyna

doi:10.3390/d12010010

Abstract

Anaerobic oxidation of methane (AOM) reduces methane emissions from marine ecosystems, but we know little about AOM in freshwater reservoirs. Lake Baikal is the world’s only freshwater reservoir where gas hydrates (GH) are found. Despite that AOM has been demonstrated in deep sediments of Lake Baikal did not reveal methane-oxidizing archaea ANME1, 2, or 3, which are responsible for AOM in marine sediments. A search for representatives Candidatus Methylomirabilis oxyfera (M. oxyfera)-like bacteria (NC10) and Candidatus Methanoperedens nitroreducens (M. nitroreducens)-like archaea (ANME-2d) has been carried out in the different types of Lake Baikal methane enriched sediments. We used different molecular biology methods including high-throughput sequencing and PCR analysis, using 16S rRNA genes as well as different functional genes of AOM (mcrA and pmoA). We found diverse M. oxyfera-like bacteria and M. nitroreducens-like archaea in various geological structures in Lake Baikal (methane seep and mud volcano), which were different from the composition of the discharged fluid. We also considered possible electron acceptors for this process in the sediments of Lake Baikal.

Highlights

Lake sediments are globally important carbon storages [1,2], but they are important contributors of methane (CH4 ) to the atmosphere [3]
Sediments of the investigated core from the methane seep Posolsk Bank (PB) were highly saturated with gas
Analysis of different genes has confirmed the presence of archaea and bacteria that most likely carry out Anaerobic oxidation of methane (AOM) processes in sediments of various geological structures in Lake Baikal, which are different in the composition of the discharged fluid and contained CHs

Summary

Introduction

Lake sediments are globally important carbon storages [1,2], but they are important contributors of methane (CH4 ) to the atmosphere [3]. 70% of atmospheric methane is of microbial origin. CH4 emissions from these environments are controlled by both methanogenesis and CH4 oxidation. Methanotrophs oxidize the resulting methane under both aerobic and anaerobic conditions, decreasing significantly the emission of this greenhouse gas into the atmosphere. In the presence of oxygen, widespread methanotrophic species of Alpha- and Gammaproteobacteria, which have the key enzyme of a methylotrophic pathway (methane monooxygenase), oxidize methane [4,5,6,7,8,9]. Aerobic methanotrophs were described within the phylum Verrucomicrobia [10]

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